The present invention relates to prosthetic devices, and in certain embodiments, to prosthetic valve leaflets that have a peripheral region receptive to tissue ingrowth.
It is well understood in human pathology that the proper functioning of cardiac and venous valves is of the utmost importance. Numerous studies have shown that diseased cardiac valves cause significant morbidity and mortality and that incompetent or destroyed venous valves often result in adverse medical conditions, especially in the lower extremities.
By preventing retrograde blood flow, the valves found throughout the venous system assist the flow of blood through the veins and returning to the heart. Venous valves are usually of the bicuspid type, with each cusp or leaflet forming a reservoir for blood, which, under pressure, forces the free edges of the cusps together to permit mostly antegrade blood flow to the heart. As a majority of venous blood flow is against gravity while a person is standing, incompetent or destroyed venous valves can cause significant medical problems in the legs, ankles, and feet. There are at least two chronic venous diseases in which venous valve incompetence is thought to be an important factor: chronic venous insufficiency and varicose vein syndrome.
Chronic venous insufficiency involves venous hypertension and chronic venous stasis due to valvular incompetence. In the United States, it has been estimated that chronic venous insufficiency (CVI) associated with skin changes and ulcers affects six to seven million people. Existing treatments for chronic venous insufficiency are less than ideal. Therapies currently available include periodic elevation of the legs, elastic support hose to compress the veins externally, and surgical repair or replacement of the valves by grafting veins from the patient's arm into the leg. These methods are variably effective. Similarly, the palliative therapies require major lifestyle changes for the patient with potentially suboptimal long-term patient compliance. Also, without repairing the valves, even if the ulcers are healed, the ulcers will recur unless the patient continues to elevate the legs and to use support hose continuously.
Varicose vein syndrome, a second chronic venous disease, involves vein dilation or enlargement. According to one estimate, varicose veins affect about 4% of the adult western population, and approximately half of this population has significant varicose vein syndrome for which treatment will be sought.
Turning now to the cardiovascular system, incompetent or destroyed heart valves are a common form of heart disease, the leading cause of death in the United States. Although reconstructive surgery has been shown to be superior to valve replacement surgery in some respects, it is difficult to perform and not always possible in every patient. As a result, the vast majority of patients with diseased heart valves undergo valve replacement surgery, which involves removing a native valve and replacing it with a prosthetic one. Prosthetic heart valves come in various shapes and sizes and can be formed with a variety of materials. Often, the design of a prosthetic valve depends on the characteristics of the valve being replaced (e.g., mitral, aortic, tricuspid, or pulmonary) and/or the size of the patient's heart.
A variety of prosthetic valves have been developed in the art to treat conditions of the cardiovascular and venous systems. One such valve is defined by a tubular wall and one or more flexible leaflets. The leaflets are integrally connected to the tubular wall and converge axially along at least one commissure. The leaflets are designed to open and close the valve in response to pressure differentials across the valve. In an open, flow-conducting configuration, the free edges of adjacent leaflets are forced apart to form a conduit through which blood can flow. In a closed, flow-restricting configuration, the free edges of adjacent leaflets are forced together to form a closure, which eliminates or greatly reduces back flow through the valve.
There remain needs for improved and/or alternative prosthetic devices, and in particular prosthetic valve leaflets, suitable for implantation in a body vessel. The present invention is addressed to those needs.